With the wider boards you'll mostly find easier, more practical, more accessible top speed ~ and more often. That's to say the newer style ride can be less technical, less demanding and often more consistant = a better chance (on average) to be "fast", c/w pure theroretical top end Vmax board that have some very wicked but narrow performance curve..
For g.e.o., it's no doubt efficiency is influenced by tail and fin dimensions, but the aspect ratio of the planing surface actually gets higher (and more theoretically efficent) as the tail gets wider and the planing surface corespondingly shorter - it's the control and longitudinal stability that are (very real) limiting factors in exploiting this. For sure, ride sensation is an issue - it's hard to beat the feeling of flying across the water on a ski rather than a door - but once we got that door to turn and maintain control it can still be potently fast !
Cheers ~ Ian